'I'anaka niul Fiijisawu in Hio oxpoiliiiuii to Sapporo during the summer of 

 ]y8l. 'J'liü metlioil is fully doscribeJ iu ineiuoir No. Tj of the iinivorsity, and 

 its Appendix ; and consequently but a brief account will liero »uflfice. 



Two pendulums were used, called for convenience 11 and C. These had 

 similar forms, but dilTercnt somewhat in construction, 'i'he H ptndulum con- 

 sisted of a hollow brass cylindor, 121(3 centimetres long and closed at Ijotli 

 ends. Near the one end was the steel knife-edgo on which the pendulum 

 rested when oscillating ; aud near the other was fixed a flat obhite-spheroidal 

 disc whose diameter was about 18'5 centimetres. The lower end Ixire a suuvll 

 wedge, whose edge, when desired, could be brought to bear upon the extremity 

 of a delicate spring, the slight displacement of which was suHicient to break 

 the circuit of the electric chronograph. 'J'hus the precise instant at which the 

 extremity of the pendulum swept pasf the end of the spring could be recorded. 

 The form of the C pendulum was exactly similar to that of H ; but its l)ob, 

 instead of being a solid brass spheroid, was made of a hollow brass shell of 

 the same outward form but filled with lead. 'J'ho modification thus introduced 

 was not originally intended, but arose from the misapprehension of the in- 

 strument maker. 



A\ lieu C was made, another pendulum exactly similar was constructed. 

 The time of oscillation of this latter pendulum (called D) had been determined 

 Ip}- Mr. Tunakadate aud sent to America to supply the place of A* which had 

 been previously sent, but injured during ti-ansportation. 



The Ü pendulum had also been injured during the Sapporo expedition ; 

 aud its upper brass disc, which was the injured portion, was now replaced by 

 a new one, so that its time of oscillation was slightly changed, as will Ix) seen 

 on comparing the old and the new results. t 



In previous expeditious Kater's reversible pendulum had been used toge- 

 ther with U pendulum. Hut the former, having been always found to give 

 unsatisfactory results, :J it was now abandoned, and tlie (" pendulum was used 

 instead. 



Two series of experiments were luade in the physical lalwratory Ix'fure 

 and after the expedition, so that any injuries done to the two pendulums 

 during the expedition might be readily detected by comparing the two set» of 

 results. 



The experimeuts at Tokio were made iu the pendulum room of the lulx)- 

 ratory. The pendulum was hung from a massive stone pillar erected iu the 

 room. The approximate position of this pillar was 



35° 42' 40' north latitude, and 

 139° 45' 4.j' east of Greenwich. 



• St-c " Appendu to mnnuir So. 6." 



f Cuiu|nirc Tabic« land Hint tlicciidof tliU pniior with tlic toUo« iu tlic "A|i|>i'iiJix tuiiicinuirMn. !>■" 



X Sou uicinoir Xo. 5 and it« Appendix. 



